Linda Thompson insists she’s just a simple country girl. “I’m the kind of person who lives under the radar,” the Memphis native tells The Post from her adopted home of Malibu, Calif., where she makes jam and keeps chickens.

But the 66-year-old — born to a “poor” family and raised a good Southern Baptist — has often been in the limelight: As a Miss USA contender, “Hee Haw” actress and significant other to some of the most high-profile men of the 1970s.

Thompson details her romances — with Elvis Presley, Bruce Jenner and songwriter David Foster — in her memoir, “A Little Thing Called Life,” out Tuesday.

She was a 22-year-old beauty queen when she met Presley — whom she’d fantasized about marrying — at a movie screening in 1972.

“I thought maybe I’d get an autograph — I had no idea I’d have 4 ¹/₂ years of loving him,” Thompson says.

The pair made out during the double feature, and the King, then 37, invited her to Graceland the next day. She moved in shortly after. At the time, Thompson was 12 credits shy of graduating from Memphis State University, but “I thought it was more important to run off with a rock star than to finish school,” she admits.

The couple was inseparable, she recalls, even in the bathroom: “I’d talk to him through the shower. I wasn’t out of his sight for a year.”

Her new life proved dazzling and odd — flying on private jets, waited on by a staff, and watching TV all night, given Presley’s nocturnal schedule.

In fact, Thompson remembers that she and the singer were in bed when they saw Bruce Jenner take gold in the 1976 Olympics. When Presley admired the athlete’s good looks, Thompson jokingly blurted out, “I’m going to marry that guy someday!”

Soon, Presley’s cheating and prescription-drug addiction took their toll. “After I had the stardust cleared from my eyes, I saw all the problems,” Thompson says, including a “dark side, [a] vicious temper, mood swings.” She left him eight months before he died in August 1977; his 9-year-old daughter, Lisa Marie, called her to deliver the news.

Heartbreak turned to romance when she met, of all people, Jenner, at the Playboy Mansion in 1979.

“He was the most easygoing, down-to-earth, healthy man,” she says. “It was the antithesis of my lifestyle with Elvis.”

The pair married in 1981, five months before their son Brandon was born. (Another son, Brody, followed two years later.) But in 1985, Jenner shocked his wife with a confession: “I identify as a woman.”

“My first inclination was, ‘Maybe we can fix this,’ ” she says.

The couple tried therapy, but the final straw was a trip to New York. When Thompson arrived at the hotel, hopeful for a reconciliation, she was greeted by her husband in a “full wig, full makeup, heels. A nice feminine dress adorning his muscular body.” They divorced in 1986.

It would be 30 years before her ex came out to the world as Caitlyn Jenner.

In 1991, Thompson married songwriter Foster, with whom she penned the Whitney Houston hit “I Have Nothing.” They divorced in 2005.

Thompson wishes her exes well and says of Jenner, “She’s a part of my heart, she’s the father of my sons.”